Process for the production of hydroxylamine



Jan. 3, 1967 H. FUEG ETAL 3,295,925

PROCESS FOR THE PRODUCTION OF HYDROXYLAMINE Filed July 9, 1963 UIMM Ill United States Patent O Claims priority, application Switzerland, July 13, 1962, 8,451/ 62 5 Claims. (Cl. 23-190) The present invention relates to a -process for the production of hydroxylamine.

It is known that nitric oxide can be reduced by hydrogen in the presence of platinum-metal-containing catalysts in an acid medium to give hydroxylamine. Furthermore, it is known that with the yield remaining unchanged, the reaction velocity can be improved if the reduction is carried out in the presence of organic compounds containing polar groups and having a medium range carbon number.

It is a disadvantage of the latter process that substances are introduced into the system which do not take part in the reaction and which may render dif'lcult the independent subsequent use of the hydroxylamine. It is a further disadvantage of this'process that the yield, which at the beginning of the reaction is 80% by weight, calculated on the nitric oxide used, cannot be maintained at a constant level, but slowly decreases.

It is the object of the present invention to provide a process for the production of hydroxylamine which is free of the above-named shortcomings and permits to obtain hydroxylamine in good yield and by a simple procedure.

Surprisingly, it has been found that the yield of hydroxylamine in the catalytic reduction of nitric oxide in the presence of platinum-metal-containing catalysts in acid solution can be maintained very high, i.e. at 80% by weight and over, with good reaction velocity, if the concentration of the hydroxylamine is maintained constant at 0.4-1.00 mol/liter of solution of a hydroxylamine salt.

Accordingly, the present invention relates to a continuous process for the production of hydroxylamine by catalytic reduction of nitric oxide by means of hydrogen in acid solution, and it more particularly consists of carrying out the reduction of nitric oxide in the presence of 0.4-1.0 mol of a hydroxylamine salt per literpof reaction solution.

The preferred catalyst for the process according to the invention is platinum, with -or without additions. Likewise, platinum alloys can be employed. Such additions or alloy components are primarily silver, mercury, lead, gold, iridium, palladium and the metals of the Vth and Vlth main groups of the Periodic Table. Mixtures of platinum with one of the indicated metals or alloys can also be employed on supports. The reaction of nitric oxide to give hydroxylamine is advantageously carried out in aqueous or alcoholic solution of sulphuric or hydrochloric acid at temperatures between the freezing point of the solution and 80 C., the best results being obtained at temperatures between 65 and 80 C. The process can be carried out at ordinary or elevated pressure.

It has been found to be particularly advantageous to perform the process in the presence of a platinum catalyst, solu'ble silver compounds being also added to the suspension of the platinum deposited on activated carbon, in aqueous solution of sulphuric acid.

It goes without saying if the concentration of hydroxylamine in the reaction solution is maintained at a constant level, the same also applies, to a certain extent, to the acidity of the solution. In the process according to the invention the pH range does not have to be kept within such narrow limits as has generally been necessary in previous processes. It is suicient to maintain the pH Patented Jan. 3,' 1967 ice between 0.5 and 3.0. If, for example, the concentration of hydroxylamine is increased beyond about 1 mol/liter of reaction solution, the rate of conversion into hydroxylamine drops somewhat and more ammonia i-s formed as an undesirable by-product.

In the following, the invention will be more fully described in a number of examples, reference being had to the accompanying drawing illustrating by way of example two devices for carrying out the process of the invention.

In the drawing:

FIG. 1 is a schematic showing of anembodiment of the device for carrying out the process according to the invention;

FIG. 2 is another embodiment, likewise shown schematically, and

FIG. 3 shows a detail of the device illustrated in FIG. 2, in top view.

Referring to FIG. 1, a vessel 10 is illustrated which is provided with a heating jacket 12 comprising inlet and outlet connections for a heating agent, designated at A and B, respectively. The vessel 10 serves for receiving the liquid in which the reaction takes place and the catalyst, both being admitted through a pipe 15 at the top of the vessel. Mounted within the vessel is a stirrer 13.

A second vessel 18 is provided in which the gases NO and H2 are introduced by individual pipes 19a, 19b leading into a mixing tube 19. From there, a pipe 14 passes the-m into the vessel 10. The gases enter at the bottom of vessel 10 and unreacted gases escape at the top through a pipe 17 arranged for that purpose.

This apparatus is used in connection with the procedures described in Examples l to 4 described hereinfbelow.

aqueous suphuric acid (concentration: 10 percent by vol-Y ume) containing 0.04 gram of `silver nitrate and 43 grams of hydroxylamine sulphate per liter and also containing 0.13 gram of Iplatinum -deposited on 1.33 grams of activated can-bon (likewise per liter). The catalyst is kept constantly in suspension by means of the stirrer 13. The temperature is maintained at 47 C. by passing hot water through the heating jacket 12. The nitric oxide .and hydrogen gases mixed in the vessel 14 (4.13 liters of NO 'and 6.25 liters lof H2 per hour and per liter of reaction solution) 4are supplied through the pipe 14 to vessel 10. 160 cc. of sulphuric acid with a concentration of 10% by volume, containing 1.33 grams/liter platinum/ activated carbon catalyst and 0.04 gram/liter of silver nitrate, saturated with hydrogen, are supplied per hour and per liter of reaction solution to the vessel 10 at the top thereof through the pi-pe 15. At the same time, 160 cc. of reaction solution per liter of the solution contained in the vessel are drawn off per hour at the lower end through the pipe 16. As mentioned before, unconverted reaction gases are carried olf through pipe 17. The size yof the vessel is so calculated that the dwell time is 5 hours. The yield of hydroxylamine is 83- A solution drawn olf contains 45.6 grams of hydroxylamine sulphate per liter.

EXAMPLE 2 0.15 gram of the platinum catalyst employed in Example 1, deposited on 1.5 grams of activated carbon, is dispersed in 1 liter of sulphuric acid with a concentration of 15% by volume which contains 57 grams of hy- `droxylamine sulphate. 16.4 liters of NO and 25.0 liters `of hydrogen are passed through per hour at a solution temperature of 25 C. 700 cc. of the reaction solution are 4drawn olf per hour and replaced Iby 700 cc. of sulphuric acid with a concentration of 15 by volume and containing catalyst and Iwhich has been saturated beforehand with hydrogen. 87-90%.

EXAMPLE 3 The alloys of 0.15 graml of platinum with 0.05 gram of mercury, on 1.5 grams of activated carbon, are dispersed in one liter of 3N hydrochloric acid which contains 60 grams of hydroxylamine chloride in solution. 4.1 liters/hour of NO and 6.25 liters/hour of H2 are passed through at 65 C. 170 cc./hour of 2 N hydrochloric acid containing the same amount of catalysts and saturated with hydrogen are supplied. 170 cc./hour of reaction solution are drawn off. Yield of hydroxylamine: 80-82%.

EXAMPLE 4 0.13 gram of platinum on 1.3 grams of activated carbon is dispersed in sulphur-ic acid with a concentration of 15% by volume and containing 70 grams of hydroxylamine sulphate and 0.01 gram of arsenious acid. 2 liters/hour of NO and 12.5 liters/hour of H2 are passed through 70 C. 340 :cc/hour of sulphuric acid with a concentration of 15% by volume and containing 0.13 gram of platinum on 1.3 gram of activated carbon and 0.01 gram of arsenious acid and saturated with hydrogen are supplied, while 340 cc./hour of reaction solution are continuously drawn o. Yield of hydroxylamine is 83-85%.

EXAMPLE The conditions correspond to those in Example 4, with the exception that an alloy consisting of equal parts of platinum .and gold is employed as catalyst in an amount of 0.15 gramper liter of reaction solution. The yield is approximately the same as in Example 4.

In FIG. 2 a device is shown, in which a reaction co1- umn is designated by 21; arranged within the column are plates 23 Iwhich are shown in top view in lFIG. 3. The plates are perforated -at 22 and contain, in the embodiment shown, 48 holes per plate. Overflow pipes 20 are provided for the passage lor liquid between the plates. 24 designates a circulation system for the reaction gases NO and H2, including a pump 26. A secondcirculation system 25 is provided for the reaction solution, including a pump 28. A heater for adjustment of the temperature of the solution is illustrated at 32.

The yield of hydroxylamine is 4 EXAMPLE 6 The process is carried out in the device illustrated in' FIGS. 2 and 3. Column 21 is supplied with 5.6 liters of NO and 9.0 liters of H2 per hour through the pipes 24a, 24b of the circulation system 24. At the start, the column 21 contains 3 liters of 10% sulphuric acid together with 0.8 gram of platinum deposited on 8 grams of activated carbon; also deposited are 0.3 gram of silver nitrate, 180 grams of hydroxylammonium sulphate. This mixture is circulated by means of the pump 28 through the pipe 25 in an amount of 200 liters/hour, while the reaction gas is circulated by Way of the pump 26 4and the pipe 24 at a rate of 700 liters/hour. The circulated reaction solution is kept at a temperature of 80 C. by the heating means 32. 1.5 liters of gas are carried olf per hour from the column through a pipe 29 and 650 cc./ hour of the reaction solution through -a pipe 30, which are replaced by adding the same amount of `fresh solution through a pipe 31.

What we claim is:

1. In a continuous -process for the production of hydroxylamine by catalytic reduction of nitric oxide by means of hydrogen in acid solution, the improvement which comprises effecting the reduction in the presence of 0.4-1.0 mol of a hydroxylamine salt per liter of reaction solution. p

2. The process according to claim 1, wherein platinum containing catalysts are employed.

3. The process according to claim 1, wherein a platinum deposited on activated carbon and impregnated with silver nitrate is employed as catalyst.

4. The process according to claim 1, wherein the reduction of nitric oxide is carried out at temperatures of -80 C.

5. The process according to claim 1, wherein the reaction is performed at a pH of 0.5-3.0.

References Cited by the Examiner UNITED STATES PATENTS 2,628,889 2/1953 Benson 23-190 2,823,101 2/1958 lockers et al. 23-190 3,009,779 11/ 1961 Wintersberger et al. 23-190 MILTON WErssMAN, Primm Examiner.

OSCAR R. VERTIZ, Examiner.

I. I. BROWN, Assistant Examiner. 

1. IN A CONTINUOUS PROCESS FOR THE PRODUCTION OF HYDROXYLAMINE BY CATALYTIC REDUCTION OF NITRIC OXIDE BY MEANS OF HYDROGEN IN ACID SOLUTION, THE IMPROVEMENT WHICH COMPRISES EFFECTING THE REDUCTION IN THE PRESENCE OF 0.4-1.0 MOL OF A HYDROXYLAMINE SALT PER LITER OF REACTION SOLUTION. 